/*
 * Copyright 2016-2018 shardingsphere.io.
 * <p>
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 * </p>
 */

package io.shardingsphere.proxy.transport.mysql.packet.command.statement.execute;

import lombok.Getter;

/**
 * Null bitmap.
 *
 * @author zhangyonglun
 */
@Getter
public final class NullBitmap {
    
    private final int reservedBitLength;
    
    private final int[] nullBitmap;
    
    public NullBitmap(final int numColumns, final int reservedBitLength) {
        this.reservedBitLength = reservedBitLength;
        this.nullBitmap = new int[calculateBitmapBytes(numColumns, reservedBitLength)];
    }
    
    private int calculateBitmapBytes(final int numColumns, final int reservedBitLength) {
        return (numColumns + reservedBitLength + 7) / 8;
    }
    
    /**
     * Set null bit.
     *
     * @param index index
     */
    public void setNullBit(final int index) {
        int bytePosition = (index + reservedBitLength) / 8;
        int bitPositionInCurrentByte = (index + reservedBitLength) % 8;
        nullBitmap[bytePosition] = 1 << bitPositionInCurrentByte;
    }
    
    /**
     * Is parameter null.
     *
     * @param index column index
     * @return is parameter null
     */
    public boolean isParameterNull(final int index) {
        int bytePosition = index / 8;
        int bitPosition = index % 8;
        return (nullBitmap[bytePosition] & (1 << bitPosition)) != 0;
    }
}
